const IS_NON_DIMENSIONAL =
  /^(-|f[lo].*[^se]$|g.{5,}[^ps]$|z|o[pr]|(W.{5})?[lL]i.*(t|mp)$|an|(bo|s).{4}Im|sca|m.{6}[ds]|ta|c.*[st]$|wido|ini)/

export let parse = (obj, selector) => {
  let outer = ''
  let blocks = ''
  let current = ''

  for (let key in obj) {
    let val = obj[key]
    if (key[0] == '@') {
      // If these are the `@` rule
      if (key[1] == 'i') {
        // Handling the `@import`
        outer = key + ' ' + val + ';'
      } else if (key[1] == 'f') {
        // Handling the `@font-face` where the
        // block doesn't need the brackets wrapped
        blocks += parse(val, key)
      } else {
        // Regular at rule block
        blocks += key + '{' + parse(val, key[1] == 'k' ? '' : selector) + '}'
      }
    } else if (typeof val == 'object') {
      // Call the parse for this block
      blocks += parse(
        val,
        selector
          ? // Go over the selector and replace the matching multiple selectors if any
            selector.replace(/([^,])+/g, (sel) => {
              // Return the current selector with the key matching multiple selectors if any
              return key.replace(/(^:.*)|([^,])+/g, (k) => {
                // If the current `k`(key) has a nested selector replace it
                if (/&/.test(k)) return k.replace(/&/g, sel)

                // If there's a current selector concat it
                return sel ? sel + ' ' + k : k
              })
            })
          : key,
      )
    } else if (val != undefined) {
      // Convert all but CSS variables
      key = /^--/.test(key) ? key : key.replace(/[A-Z]/g, '-$&').toLowerCase()
      if (typeof val === 'number' && !IS_NON_DIMENSIONAL.test(key)) {
        val = val + 'px'
      }
      // Push the line for this property
      current += key + ':' + val + ';'
    }
  }

  // If we have properties apply standard rule composition
  return (
    outer +
    (selector && current ? selector + '{' + current + '}' : current) +
    blocks
  )
}